This invention relates to the measurement of intensity in shot peening and shot blasting processes. Shot peening is a well established process for increasing the fatigue life and strength of metal products. In the shot peening process, the product undergoing peening is subjected to a stream of shot. The intensity of the peening process is a function of many factors, including the size and the velocity of the shot. Accordingly, it is necessary to regulate and confirm peening intensity, usually by the so-called Almen process, which uses Almen strips subjected to peening, and then measured by a gage as described in U.S. Pat. No. 2,350,440. In this process, a thin metal strip is placed on a fixture and peened for a predetermined time. Although the strip is initially flat, when subjected to the shot stream during peening, the strip will become curved. The amount of curvature is a function of peening intensity. Accordingly, by measuring the deflection of the test strip from its initial flat condition, an indication of peening intensity is determined.
Blast cleaning is a similar process in which an abrasive grit is blasted onto a surface to remove paint, etc. Since blast cleaning at high intensities may damage the surface, it is also necessary to determine the intensity. This is done similarly to the aforementioned process for measuring the intensity of shot peening.
Some products, which must be peened, have complex shapes such as narrow crevices or cavities. Oftentimes these cavities are points of increased stresses so that the area around these cavities will benefit from peening. The standard Almen strip, however, is too large to fit in many of these cavities, therefore, peening intensity cannot be easily confirmed. Oftentimes, the peening intensity in such cavities depends upon the peening media ricocheting off of the product or off of the walls of the peening chamber in which the peening takes place. Although the peening intensity inside of the cavity will be less than the intensity on the remainder of the product, the actual intensity is difficult to confirm.
The standard Almen strip is approximately three inches long and three quarters of an inch wide. Clearly, standard Almen strips are too large to fit into small crevices and cavities. Accordingly, so called “mini-strips” have been proposed in which the strips are one eighth of an inch wide and either one or two inches long. These mini-strips are small enough to fit into the cavities and crevices where a measurement of intensity is desired. These mini-strips however, are impossible to be measured using a standard Almen gage. The standard Almen gage uses contact balls to support the Almen strip but the mini-strips are too narrow to rest on all four contact balls. For this reason, a new gage providing stable measurements of the deflection of a mini-strip is required.